In the conventional technique for the manufacture of semiconductor devices, a slice of semiconductor material (p- or n-type) accepts a relatively thin layer, typically 5,000 to 10,000 A., of an insulating film grown or deposited on one or both of its surfaces. A layer of photoresist material is then spun onto the insulating layer of one side, and is subsequently exposed to UV light through a mask having openings corresponding to those areas on the semiconductor slice where it is desired to generate semiconductor junctions. After exposure of the photoresist material through the mask, the mask is removed and the layer of photoresist is developed and processed by means of a suitable solvent, exposing select areas of the underlying insulating layer. A wet acid-based dip is then used to etch the insulating layer from the surface of the semiconductor slice in the exposed areas, the remaining photoresist material serving as an etch-mask for the surface covered by it. Following the wet etching process, a water rinse and a drying step are implemented. The remainder of the photoresist material is subsequently removed, followed by an acid dip required for the removal of inorganic residues. The photoresist material can also be removed by a plasma process utilizing the halocarbon-oxygen gaseous mixtures disclosed by the present inventor in his U.S. Pat. application, Ser. No. 173,537, filed Aug. 20, 1971. Following a further drying step, diffusion of dopant material into the exposed areas of the semiconductor slice (where there is no insulating layer) is commenced to produce a predetermined junction.
Among the problems and drawbacks associated with the etching step used in this particular technique are:
(1) Physical degradation of a photoresist etch mask. PA0 (2) Finite chemical degradation of a metallic etch mask. PA0 (3) Impairment of line-line resolution due to (1) and/or (2). PA0 (4) Enhanced undercutting effects creating undesirable slopes of the etched channel. PA0 (5) Severe chemical degradation (corrosion) of underlying metalization layers; e.g., aluminum in multileveled structures. PA0 (6) Slow and technically elaborate etching of silicon monoxide and silicon nitride. PA0 (7) Required post-etch water rinse and drying steps invariably reducing production yields. PA0 (8) Short shelf-life of etching solution due to inevitable contamination. PA0 (9) Generally very hazardous to personnel and undesirably polluting.
Accordingly, the general object of the present invention is to provide an improved process and new material that overcome the aforementioned problems and provide uniform etching reactions at a rapid rate.